Optically Transparent, Ultra-Broadband, and Water-Based Microwave Meta-absorber with ITO Metasurfaces

A transparent in visible wavelengths and ultrabroadband microwave meta-absorber (MMA) based on indium tin oxide (ITO) metasurfaces and a water layer is proposed. After optimizing a series of structural parameters, the proposed MMA can achieve ultrabroadband absorption with an absorption efficiency of more than 90%, covering the frequency range of 9.44-120.92 GHz and a relative absorption bandwidth of 171%. Furthermore, the absorber has many advantages, such as optical transparency, polarization insensitivity, and wide-angle absorption for transverse electric (TE) and transverse magnetic (TM) polarization waves. Moreover, the proposed MMA with 15 × 15 unit cells was fabricated and tested. The fabricated MMA performs well in microwave absorption, as demonstrated by the well-matched experimental results with numerical simulations. These extraordinary advantages mentioned above show that this type of MMAs can be applied in the fields of electromagnetic (EM) stealth, optical windows, and energy collection in the future.